Hakucho

Hakucho was the first Japanese X-ray astronomy satellite;
it was named "swan" in Japanese because one of the most powerful cosmic
X-ray sources is Cygnus X-1. As in the case of many other X-ray satellites
deployed around this time, Hakucho was designed to study and monitor transient
(quick-changing) phenomena, with special emphasis on X-ray bursts in the
energy range 0.1–100 keV. It was known prior to launch as Corsa-B.
Hakucho stopped operating in April 1985.